Current wet shave razors typically include a razor cartridge and a razor handle.
The razor cartridge components typically include some of the following elements: one or more razor blades having a blade edge to perform the cutting of hair, a lubricating body/strip/ring, a cap, a housing, a frame, a clip, a guard, a cartridge connecting structure, or any number of each or combination thereof.
The razor handle may comprise a button, a handle grip, a cartridge connecting structure, or any combination thereof. Typically, the handle components may be formed of some combination of elastomeric and hard plastic materials. Razor handles may also comprise metallic parts, for example, stainless steel parts.
Razor cartridge components have exterior surfaces, many of which contact a user's skin during shaving. The interaction of these contacting surfaces with skin may generally play a significant role in the performance of the razor.
The inherent surface properties of stainless steel are not always optimal for the task of shaving. For example, razor blades are a typical example of shaving articles that comprise a stainless-steel substrate for which it is already known to improve their shaving characteristics by addition of layers, such as coatings, to the exterior surface thereof. Such layers may be associated with optimizing, for example, edge strength, tip shape, wear resistance, and/or blade glide (i.e. lubricious character or low friction) etc.
External layers that reduce friction with a user's skin or hair are of particular interest, for example by increasing article lubricity. A razor blade with a low coefficient of friction exhibits reduced cutting forces for beard hairs or other types of hair fibers. A reduced cutting force can significantly improve shaving attributes (safety, closeness and comfort). The concept of cutting force can be generally understood as how readily a blade passes through a hair stem during cutting. The more readily a blade cuts a hair the less tug and irritation may generally be expected.
Known coatings for razor blades may be comprised of inorganic materials for hardness and corrosion resistance, such as diamond, amorphous diamond, diamond-like carbon (DLC) material, nitrides, carbides, oxides, and ceramics in general.
Other known razor coatings may be organic, for example comprising polymers. One such polymer is polytetrafluoroethylene (PTFE), a coating of which can provide a low coefficient of friction to the coated article.
In addition to razor blades, it is also known that other razor cartridge components (e.g., blade clips, frame, housing, guard, cap, etc.) may comprise stainless steel surfaces that contact a user's skin and play a role in the shaving performance of the razor. Blade retention clips, housings, guards or caps etc. with lower coefficients of friction can glide more comfortably across a user's skin, reducing skin pull or improving skin manipulation.
Furthermore, razor handles have multiple surfaces that are contacted by a user's skin (e.g., hands on a grip). While razor handle surfaces are normally comprised of anti-slip, rubber or elastomer type materials or coatings for better gripping, they may also comprise stainless steel surfaces, the inherent surface properties of which can also be optimized.
In terms of increased lubricity of surfaces, such as for razor blades, a variety of PTFE coating processes are suggested in the art. For example, aqueous dispersion PTFE (spraying, spin coating and dipping), organic dispersion of PTFE, and vacuum based processes such as sputtering or Chemical Vapor Deposition (CVD). Known coating techniques such as painting, droplet evaporation, spray coating, spin coating, and dip coating, rely on physical adsorption.
The application of PTFE to razor blades, or other substrates, can be complex. This may lead to manufacturing costs, and/or less than desired coating efficacy. In addition, a less than desired coating fixation may result and lead to premature loss or peeling of the coating from the substrate. The latter may reduce the useful lifetime of the blades or result in skin irritation. PTFE, is also relatively inert and a resultant low adhesion to substrates means only weak, physical interactions bind it to surfaces. Such coatings may thus be prone to layer degradation, surface wear and mechanical failure.
An example of a razor having PTFE applied by way of an aqueous solution is found in U.S. Pat. No. 6,866,894, hereby incorporated by reference. The aqueous solution is applied to the surface of blades, which are then heated to a temperature that melts the solids of the aqueous solution.
Other coating technologies are known. For example, WO 2008123957 discusses adhesion of organophosphorus compounds to a cutting edge for surface modification. The organophosphorus layer on the cutting edge is in the form of a self-assembled monolayer. Also, WO 2014197667 discusses application of liquid-infused surface materials (LISM) to surfaces of razor components. The LISM layers are said to be generally abrasion-resistant, long-lasting or non-erodible, desirably elevating shaving performance, such as glide, comfort, rinsing, and cleanliness, while also simplifying the manufacturing process. WO 2015161996 describes a hard coating for blades having particles incorporated therein having covalently pendant hydrophilic polymer chains attached thereto to provide a high wearing lubricous coating. U.S. 20120015138 describes the use of a diazonium salt bearing initiator for grafting a polymer layer onto to an under-layer.
In line with the above discussion it is generally desirable to improve or enhance shaving performance of shaving articles. As compared to the prior art, it is desirable to seek new, and preferably optimized, surface enhancing layers and/or methods of applying such layers (e.g. as coatings), while maintaining or improving shaving article performance.